Cost: $150 average
MPG Improvement: 10 to 20 percent Mile Per Gallon (MPG) Meters are nothing new. In fact, they have been used by hypermilers for a number of years. Scan Gauge II is probably one of the more popular of the model choices. However, just because it has been around awhile doesn't mean that there hasn't been some pretty significant improvements, such as a smaller size, larger display, multicolor LEDs to match interior lighting, data logging, and a full year warranty.
The way it works is it tells you the MPG figures that your vehicle is achieving in real-time as you drive. This means that you can see for yourself just how big of a difference a variety of situations makes in your vehicle's fuel economy, such as stop and go traffic, hills, cold weather, hot weather, etc. An MPG meter takes all the guess work out of knowing how to drive eco-consciously.